Computer systems come in a variety of topologies. Systems that include multiple data processing modules (or nodes) often have complex topologies. The interconnection assemblies that connect the modules of such topologies are often complicated, as well. In particular, it is a demanding task for an interconnection assembly to provide several connections (or links) to each module, as required by certain systems having mesh-shaped and torus-shaped configurations.
A typical multi-module computer system has an interconnection assembly that includes a backplane, module connectors and flexible wire cables. The backplane is a rigid circuit board to which the module connectors are mounted. Each module is a circuit board that electrically connects with the backplane when plugged into one of the mounted module connectors. The flexible wire cables connect with the backplane to configure the system into a network topology having a particular size.
The network topology of a typical multi-module computer system is expandable by adding another backplane and reconnecting the flexible wire cables to configure the system into a larger network topology. Generally, the topology of the system is expanded by several modules at a time. For example, one such system having a 4xc3x974xc3x974 torus topology is expanded by adding a 16-module backplane and reconnecting the flexible wire cables to expand the system to a 4xc3x974xc3x975 torus topology. As another example, in a system having 2-D mesh topology, the minimum unit of expansion is a backplane that adds four modules to the system. Some systems permit expansion by hot-plugging, i.e., plugging and unplugging cables to expand the topology of the system while the power remains on.
Examples of some conventional systems that are expandable by several modules at a time are the Paragon made by Intel Corp., of Santa Clara, Calif., and the Cray T3D/T3E made by Cray Research Corp., of Eagan, Minn.
Conventional multi-module systems generally do not allow incremental expansion in units of single modules. Rather, such systems typically expand by increasing the topology to the next largest regular network (e.g., adding a 16-module backplane and reconnecting cables to expand a system from a 4xc3x974xc3x974 torus topology to a 4xc3x974xc3x975 torus topology).
In general, the poor extensibility of conventional machines is due to two factors. First, it is often a laborious and error prone process to expand the system at all. Hence, cabled systems are expanded generally by several modules at a time to avoid having to expand the system again in the near future. Second, some conventional machines also employ regular routing algorithms, such as e-cube (or dimension-order) routing, that only work in a regular (complete) torus or mesh network. Accordingly, such systems could not be expanded incrementally.
The present invention is directed to techniques for incrementally expanding the topology of a multi-module system by connecting modules in a configuration, and changing the configuration remotely. That is, a single module can be added or deleted from the configuration by remotely switching from conducting paths that provide end-around electrical paths (i.e., paths connecting to a single backplane) to conducting paths that provide pass-through electrical paths (i.e., paths extending between two backplanes). Accordingly, the topology of the system can be incrementally changed by a single module by remotely switching conducting paths.
Preferably, the configuration has the capability to take the form of a logical three-dimensional torus. A true torus is at least three modules deep in each dimension, coupled in a loop. When the depth of the configuration drops below three modules in at least one dimension, the configuration is considered a degenerate torus. For simplicity, the term xe2x80x9ctorusxe2x80x9d is used hereinafter to refer to either a true torus (one that is at least three modules deep in each dimension) or a degenerate torus (one that is less than three modules deep in at least one dimension).
A preferred module connection assembly that is suitable for the invention includes two backplanes, a first set of module connectors for electrically connecting modules to one of the backplanes, and a second set of module connectors for electrically connecting modules to the other backplane. The assembly further includes configuration controllers. Each configuration controller selects between end-around electrical paths that electrically connect multiple module connectors of the first set to each other, and pass-through electrical paths that electrically connect module connectors of the first set to module connectors of the second set.
Each configuration controller may operate as a remotely configurable switch that configures a topology formed at least in part by the backplanes and the module connectors. Each configuration controller may include a configuration board that moves between an end-around position connecting nodes on a common backplane and a pass-through position connecting nodes on two backplanes. The configuration controller may further include an actuator that moves the configuration board between the end-around position and the pass-through position. In one embodiment, the actuator is remotely controlled according to an actuator signal.
The assembly may further include a backplate that physically supports the first and second backplanes such that the configuration board is disposed between the backplate and the two backplanes.
Preferably, each configuration board includes end-around pads that electrically connect with the end-around electrical paths, and pass-through pads that electrically connect with the pass-through electrical paths. The backplanes preferably include backplane pads that electrically connect with their respective module connectors. The end-around pads of the configuration board align with the backplane pads of the first backplane when the configuration board is in the end-around position. Similarly, the pass-through pads of the configuration board align with the backplane pads of the first and second backplanes when the configuration board is in the pass-through position.
Each of the end-around and pass-through electrical paths may be cableless paths formed exclusively of rigid metallic material. The paths may be made exclusively of etch, contacts, and springs.
Each backplane provides conducting paths formed preferably of similar rigid metallic material. The conducting paths of the backplanes and the configuration boards combine to form links that connect module connectors of the same backplane when the configuration boards are in their end-around positions, and different links that connect module connectors of different backplanes when the configuration boards are in their pass-through positions. When one configuration board is moved from its end-around position to its pass-through position, at least one module connector is added to the topology. In particular, one end-around link is broken, and two pass-through links to at least one new module connector are formed.
The backplanes connect with modules through the module connectors. Each module can be a fabric routing node such that a network router is formed. Alternatively, each module can be a data processing module such that a multicomputer system is formed.
The backplanes and configuration controllers form a backplane structure that provides links which electrically can connect the plurality of module connectors in a logical torus having multiple dimensions. Each link preferably includes a pair of unidirectional channels. Each channel preferably carries differential signals. The preferred configuration controllers are circuit boards that operate as switches which are remotely controlled to electrically connect the plurality of module connectors in the logical torus. In one embodiment, the logical torus is three dimensional.
The preferred backplane structure electrically connects the module connectors in an interleaved manner. In particular, the module connectors are disposed physically in row segments on the backplane structure. The row segments are disposed physically on the backplane structure in a two dimensional array. The backplane structure electrically connects the row segments in an interleaved manner in each of the two dimensions of the array. The backplane structure may further connect the module connectors in each row segment in an interleaved manner in a third dimension such that the backplane structure electrically connects the module connectors in an interleaved manner in three dimensions.
The module connection assembly provides links that connect the modules of a multi-module system together. An operator can change the topology of the system remotely by switching one or more of the configuration controllers of the system. In particular, the operator can incrementally expand the system by remotely switching just one of the configuration controllers.
The module connection assembly alleviates the need for using wire cables. Accordingly, the operator does not need to search for the correct cables in a maze of cables, plug and unplug cables, and work with cables in tight places. Additionally, the present invention allows for higher connection density, i.e., connections per inch or board perimeter than that of a typical conventional cabled system.
Furthermore, the module connection assembly is remotely switchable so that the operator is not hindered by space limitations. Accordingly, the topology can be reconfigured without needing to gain access to the back of the system. Also, with remote actuation, it is easy to make sure that the correct paths are being modified when changing the topology of the system. That is, the remote activation reduces the likelihood of connection errors (e.g., plugging a cable into an incorrect location, or incorrectly plugging a cable into a correct location). Additionally, the cost per signal is substantially lower than with a cable. Furthermore, signal integrity is preserved, i.e., the signal remains in a good 100-ohm differential transmission line environment through the connector. In contrast, a cable, and its two connectors, usually involve a significantly greater impedance discontinuity.